In-orbit performance of the soft X-ray imaging telescope Xtend aboard XRISM
Hiroyuki Uchida, Koji Mori, Hiroshi Tomida, Hiroshi Nakajima, Hirofumi Noda, Takaaki Tanaka, Hiroshi Murakami, Hiromasa Suzuki, Shōgo Kobayashi, T. Yoneyama, Kouichi Hagino, Kumiko Nobukawa, Hideki Uchiyama, Masayoshi Nobukawa, Hironori Matsumoto, Takeshi Go Tsuru, M. Yamauchi, Isamu Hatsukade, Hirokazu Odaka, Takayoshi Kohmura, K. Yamaoka, Tessei Yoshida, Yoshiaki Kanemaru, Daiki Ishi, Tadayasu Dotani, Masanori Ozaki, H. Tsunemi, Keitaro Miyazaki, Kohei Kusunoki, Yoshinori Otsuka, Haruhiko Yokosu, Wakana Yonemaru, Kazuhiro Ichikawa, Hanako Nakano, Reo Takemoto, Tsukasa Matsushima, Reika Urase, Jun Kurashima, Kotomi Fuchi, Kaito Hayakawa, Masahiro Fukuda, Shun Inoue, Yuma Aoki, Kouta Takayama, T. Sako, Marina Yoshimoto, Kohei Shima, Mayu Higuchi, Kaito Ninoyu, Daiki Aoki, Shun Tsunomachi, Takashi Okajima, M. Ishida, Yoshitomo Maeda, Takayuki Hayashi, Keisuke Tamura, Rozenn Boissay-Malaquin, Toshiki Sato, Mai Takeo, Asca Miyamoto, Gakuto Matsumoto, Megan E. Eckart, Natalie Hell, Maurice A. Leutenegger, Kiyoshi Hayashida
Abstract
Abstract We present a summary of the in-orbit performance of the soft X-ray imaging telescope Xtend onboard the X-Ray Imaging and Spectroscopy Mission (XRISM), based on in-flight observation data, including first-light celestial objects, calibration sources, and results from the cross-calibration campaign with other currently operating X-ray observatories. XRISM/Xtend has a large field of view of ${38{^{\prime }_{.}}5}$ $\times$ ${38{^{\prime }_{.}}5}$, covering an energy range of 0.4–13 keV, as demonstrated by the first-light observation of the galaxy cluster Abell 2319. It also features an energy resolution of 170–180 eV at 6 keV, which meets the mission requirement and enables us to resolve He-like and H-like Fe K$\alpha$ lines. Throughout the observation during the performance verification phase, we confirm that two issues identified in the Soft X-ray Imager (SXI) onboard the previous Hitomi mission—light leakage and crosstalk events—are addressed and suppressed in the case of Xtend. A joint cross-calibration observation of the bright quasar 3C 273 results in an effective area measured to be $\sim$420 cm$^{2}$ at1.5 keV and $\sim$310 cm$^{2}$ at 6.0 keV, which matches values obtained in ground tests. We also continuously monitor the health of Xtend by analyzing overclocking data, calibration source spectra, and day-Earth observations; the readout noise is stable and low, and contamination is negligible even one year after launch. A low background level compared with other major X-ray instruments onboard satellites, combined with the largest grasp ($\Omega _{\rm eff}\sim 60$ cm$^2$ deg$^2$) of Xtend, will not only support Resolve analysis, but also enable significant scientific results on its own. This includes near-future follow-up observations and transient searches in the context of time-domain and multi-messenger astrophysics.